1. Field of the Invention
The present invention relates to a diffusion-bonding method of fabricating a single-piece part for a turbine engine, such as an airplane turboprop or turbojet, the part being constituted, for example, by a power transmission shaft between the main shaft of a turbojet and an accessory gearbox (AGB) for driving accessory equipment of the engine.
2. Description of the Related Art
The AGB shaft is relatively fine and long, with a length of the order of one meter for large diameter engines, and it is generally made in two portions that are arranged end-to-end for reasons of mechanical strength and of withstanding vibration. The adjacent ends of these two portions are guided and centered in rotation by an intermediate bearing that allows the frequencies of resonant modes of vibration to pass.
Proposals have already been made to fabricate such a shaft as a single piece by diffusion bonding. That method consists in forming a blank for the shaft about a rotating cylindrical mandrel, by taking at least one metal wire from a reel or a spool and winding it onto the mandrel so as to form a plurality of coaxial and superposed annular layers of metal wire that surround the mandrel, each of which layers is made up of a plurality of touching turns, and then in subjecting the blank to diffusion bonding treatment by hot isostatic pressing (HIP) in appropriate tooling. The resulting part is a single piece and may be subjected to machining for finishing, should that be necessary.
It is also known to reinforce that type of part with metal-coated ceramic fibers that are wound as one or more layers on the mandrel between two layers of metal wires, respectively an inner layer and an outer layer.
Earlier patent applications FR 11/50194, FR 11/51706, and FR 11/52129 in the name of the Applicant describe methods of the above-specified type.
Nevertheless, the methods of the prior art do not make it possible to fabricate parts of non-circular section since it is difficult or indeed impossible to wind a metal wire around a mandrel of a shape that is not cylindrical.
A particular object of the invention is to provide a solution to this problem that is simple, effective, and inexpensive.